Apparatus utilizing sonic vibrations to facilitate the movement of particulate material along a sloping surface

ABSTRACT

An apparatus for initiating and facilitating sliding of material along a sloping bottom comprises upper and lower members secured on opposite sides of the bottom and covering an opening provided therein, the upper member being a gas-permeable member. A sound transmitter carried by the lower member opens into a chamber formed by the two members and is directed towards the gaspermeable upper member. The bottom provides together with the elements thus supported thereby a vibrationable unit and forms a fixedly mounted diaphragm thereof in order to vibrate when material supported by the bottom is activated by sound oscillations produced by the sound transmitter.

d States Patent l l olm Jan. 25, 1972 [72] Inventor: Bengt L. Holm,Malmo, Sweden [73] Assignee: Kockums Melcaniska Verkstads Aktiebolag,Malmo, Sweden [22] Filed: Feb. 2, 1970 [21] Appl. No.: 7,623

[30] Foreign Application Priority Data Feb 3, 1969 Sweden ..1383/69 [56]References Cited UNITED STATES PATENTS 2/1967 Caldwell ..222ll95 1/1966Bodine ..259/DIG.43

FOREIGN PATENTS OR APPLICATIONS 214,889 8/1967 Sweden ..222/196 OTHERPUBLICATIONS E. B. Steinberg, Ultrasonics in Industry lO/65/All PrimaryExaminer-Samuel F. Coleman Assistant ExaminerNorman L. Stack, Jr.An0rneyEugene E. Geoffrey, Jr.

[57] ABS'IIRACT An apparatus for initiating and facilitating sliding ofmaterial along a sloping bottom comprises upper and lower memberssecured on opposite sides of the bottom and covering an opening providedtherein, the upper member being a gas-permeable member. A soundtransmitter carried by the lower member opens into a chamber formed bythe two members and is directed towards the gas-permeable upper member.The bottom provides together with the elements thus supported thereby avibrationable unit and forms a fixedly mounted diaphragm thereof inorder to vibrate when material supported by the bottom is activated. bysound oscillations produced by the sound transmitter.

7 Claims, 2 Drawing Figures APPARATUS UTILIZING SONIC VIBRATIONS TlFACllLlTATE TlhlE MOVEMENT 0E" PARTTCULATE MATERIAL ALONG A SLOPINGSURFACE This invention relates to an apparatus for initiating andfacilitating sliding of material along an essentially plane slopingsurface.

in containers intended for storage of pulverulent, granular or viscousmaterial it is as a rule advisable to empty the materials by lettingthem slide downwards along a sloping bottom or bottom portion (slopingconveying plate) under the action of gravity only. The same method isapplied in principle in many cases for conveying materials from acontainer down into a well or chute or an opening of a relatively smallcross-sectional area.

For economical reasons it is intended not to give the sloping bottom, orthe sloping bottom portions greater inclination than necessary, sincethe space beneath the bottom or the bottom portions may very seldom beused for useful purposes. It is, however, necessary to pay due attentionto the fact that the slope must be sufficient in order that thematerials may not get stuck on account of their adhesion to the bottomportions or for other reasons.

A known method of preventing such difficulties is to impart vibrationsto the bottom or to a part thereof. For that purpose it is possible toprovide sufficient amplitudes for instance by striking the bottom with ahammer or by using continuously operating mechanical vibrators. Anothermethod is to blow air or another gas into the materials, generally frombeneath, so that they are loosened and consequently more easily movable(fluidized). The latter method is efficient in particular when it isimportant to keep the materials easily movable within relatively limitedzones, for instance around the outlet opening in transport containers.For bigger containers of the silo type there would be requiredconsiderable quantities of air or other gases in order to providesufiicient mobility along the large surfaces of which the sloping bottomportions consist. Furthermore, it would entail considerable difficultiesand costs to make these surfaces or the greater part thereof permeablein the required manner, i.e., with very closely spaced openings, forinstance by means of porous bottom plates, cloth or the like, since theweight of the quantity of materials stored in the container places greatdemands on the strength of the bottom.

The present invention relates to an apparatus for initiating andfacilitating the sliding of materials along an essentially plane slopingbottom or one or more essentially plane portions of a bottom, saidapparatus combining a relatively simple construction and the property ofbringing about an efficient loosening or fluidizing effect on thematerial carried by the bottom, over a large surface withoutconsiderable consumption of air. For this purpose, there is provided anapparatus utilizing on one hand the loosening or fluidizing efiect of agas pressed into the materials, preferably air, which is vibrated atsound frequency by means of a sound transmitter, and on the other handthe reaction of the pressure variations generated thereby when the gasflow thus vibrating is pressed into the materials through the gaspermeable bottom portion, which must of course be so strong and of sucha construction that it will withstand the high-static pressure generatedby the materials located on top of the bottom. The vibrations, whichappear as pressure variations, are attenuated during the flowing of thegas through the material and are transformed into kinetic energy in thevarious material particles, which are thus more easily separated fromeach other as well as from the surrounding walls.

According to the invention there is provided an apparatus for initiatingand facilitating the sliding of materials along an essentially planesloping bottom, wherein there is a cap rigidly fixed to the underside ofthe bottom and carried thereby, said cap being disposed over an openingprovided in the bottom spaced from the defining margins thereof, saidopening being covered on the top of the bottom by a gas permeable bottommember which together with the cap defines a chamber into which thereopens a sound transmitter carried by the cap and directed towards thegas permeable bottom member, said transmitter being intended to activatethe materials on the bottom by loosening them and activating saidmaterials by means of sound oscillations from the sound transmitter, andwherein said cap provides together with the bottom a vibrationable unit,said bottom forming a fixedly mounted diaphragm.

Further objects and advantages of the invention will be described ingreater detail in the following with reference to the accompanyingdrawings, in which FIG. 1 is a vertical sectional viewof a container ofmaterials having a sloping bottom and embodying the apparatus accordingto the invention, the members covering the opening in the bottom, thepermeable bottom portion, and the cap with the sound transmitter beingshown in side view; and

FIG. 2 is a fragmentary plan view of the bottom portion of thecontainer.

The container shown in the drawings comprises sidewalls l0 and anessentially plane sloping bottom (or bottom portion) 11 as well as adischarge opening -12 located below and is presupposed to be filled witha pulverulent, granular or viscous material which is indicated at 13. Inthe bottom (the sloping conveying plate) 111 which slopes towards thedischarge opening 12 there is provided a circular opening which iscovered on the underside of the bottom with a frustoconical outer cap 14disposed as an outer lid or cover over the opening, and on the top ofthe bottom with a bottom member made as a gas-permeable frustoconicalinner cap 15, said caps defining a space between them and being fixed tothe bottom by means of clamping rings 16 and 17 having the same diameterand being clamped opposite each other at opposite sides of the bottomlll concentrically with the opening by means of a screw and boltconnection 18, so that the caps together with the bottom form amechanically stable homogeneous construction. On the outer cap 14 a pipestub 19 is fixed with one of its ends, and the interior of said pipestub is in communication with the space defined by the caps 14 and 15through the end of the pipe stub connected with the outer cap, while theother end of the pipe stub is closed by means of an end plate 20carrying a sound transmitter of the pneumatic siren type having adiaphragm valve housing 21 located on the outside of the end plate 20and a resonator horn 22 located inside the pipe stub l9, said hornhaving its opening directed towards the end of the pipe stub 19 which isconnected with the outer cap 17. To the diaphragm valve housing 21 thereis connected a line 23 for supplying gas under pressure (generallycompressed air) which is used for operating the sound transmitter. This.gas is supplied to the space defined by the outer cap 14, the inner cap15, the pipe stub 19 and the end plate 20 and having a vide dischargesurface formed by the mantle surface of the frustoconical inner cap 15.For that purpose the inner cap consists of a number of bars (not shown)which are fixed to the clamping ring T7 and a ring 24 concentricaltherewith and being of minor diameter and extending along the generatrixbetween these two rings, and a gas-permeable cloth 25, for instance orPerlon, covering and resting on the bars. The bars are preferably sewninto the cloth. The ring 24 is covered by a tightly sealing lid 26 whichis fixed by means of screw and bolt connections 27. The structure of thegas permeable inner cap 15 is of such a kind and of such dimensions thatneither the cloth nor the bars are subjected to greater stresses thancan be received and carried by these elements. This is made possible byrelatively weak dimensions, largely thanks to the conical shape of theinner cap. Of course, the inner cap may have another shape, e.g.,spherical, but in that case the manufacture thereof will become morecomplicated.

The space defined by the caps 14 and TS forms an expansion volume forthe vibrating gas flow which is discharged by the sound transmitter 21,22 through the resonator born 22 when compressed air is supplied throughthe line 23. By means of the vibrating gas flow passing through thegas-permeable wall of the inner cap 15 formed by the cloth 25 and thesupporting bars, and penetrating into the material 13 which is set inmotion, as described above, within an area adjacent the inner cap. Inaddition, however, the unit formed by the bottom and the soundactivating device rigidly secured thereto will vibrate in time with thesound oscillations as a result of the momentaneously alternatingresistance at the penetration of the gas into the boundary layer betweenthe cloth 25 and the material 13. These vibrations are transmitted onaccount of the rigid connection between the sound activation device andthe bottom directly to the latter, which forms a fixedly mounteddiaphragm.

In order to increase the reaction power from the pressure variations itis important that the sound wave, which propagates essentiallyspherically from a point immediately inside the opening of the resonatorhorn 22, as shown in dot and dash lines 28 in FIG. 1, meets thereflecting material along a boundary surface whose shape coincides withthe wave front. At a certain point of time the whole surface is then hitby a pressure wave of the same phase. The inner cap 15, which determinesthe shape of the boundary layer by means of its gas permeable cloth 25,is frustoconical in the embodiment described here, which provides for arelatively good coincidence with the shape of the wave front incombination with a very good strength against the pressure forces actingfrom the interior of the container towards the inside cap. A sphericalcap may be used, as mentioned above, and is slightly more ideal in viewof a reflection effect of almost correct phase. It is, however,considerably more complicated to manufacture. It should be mentioned inthis connection that a reflection of almost correct phase isparticularly important in the cases where materials in the containerhave become densely packed in the area adjacent the inner cap. Thepercussion effect arising against the material during such reflectionmay form cracks, which may spread also in relatively hard layers and mayconsequently create the sliding effect aimed at.

In order to increase the loosening and fluidizing effect exerted on thematerial 13 in the container it may be advisable to provide a line 29 tothe space defined by the outer cap 14 and the inner cap 15 in order tosupply extra pressure gas (usually compressed air) to the said space.This added gas will then be discharged through the cloth 25 togetherwith the gas vibrating at sound frequency from the sound transmitter 21,22 and pressure oscillations will be imparted thereto by the sound wavespropagating from the opening of the resonator horn 22. In the line 29there may be provided a valve making it possible either to supplyadditional gas in the manner just described, or to connect the spacedefined by the outer cap and the inner cap, with the surroundingatmosphere. In the latter case the material 13 in the container will beaffected by the percussion effect provided by the sound oscillations andthe consequent vibration of the bottom 11 but gas will not be pressedinto the materials, which it may be desirable to avoid in order that thematerials may not create a great deal of dust.

The apparatus proposed according to the invention for initiating andfacilitating the sliding of materials along a sloping bottom has threefunctions, the internal relation of which is dependent upon theconstructional embodiment of the apparatus:

l. Loosening the material in the container by pressing gas underpressure into it.

2. Percussion effect against the material in the container in itsboundary surface against the inner cap by reflection of essentiallycorrect phase.

3. Vibrations generated by the reaction from the percussion effect inthe unit formed by the bottom and the sound activating means rigidlyfixed thereto.

When a line 29 is arranged and provided with a valve of the kinddescribed above the effect indicated under item I may be left out but inthat case vibrations which are sufficiently efficient for many types ofmaterials may be obtained through the effect according to items 2 and 3.

In order to avoid that the gas introduced into the materials may have topass upwards through the whole quantity of material in the container,air outlets may be provided in the walls of the container at suitabledistances above the activation means.

As mentioned above, the embodiment shown may be modified, and additionalmodifications may be made within the scope of the appended claims.

I claim:

1. Apparatus for initiating and facilitating the sliding of particulatematerial along an essentially plane sloping surface, comprising acontainer having a bottom outlet and a resilient sloping memberadjoining said'outlet and forming said surface, said member having anopening spaced from the defining margins thereof, a lower cap rigidlyfixed to the lower side of said member and carried thereby, said lowercap underlying and closing said opening, a gas-permeable member coveringsaid opening on the upper side of said sloping member, saidgas-permeable member and said lower cap defining a chamber, and a soundtransmitter carried by said lower cap, said sound transmitter openinginto said chamber and being directed toward said gas-permeable member toactivate said material by loosening and activating the material by meansof sound oscillations produced by said sound transmitter, said lower capand said gas permeable member imparting sonic vibrations to saidresilient sloping member which thereby forms a diaphragm further aidingin the movement of said particulate material.

2. Apparatus as claimed in claim 1, wherein said gas-permeable memberforms a supporting surface for the material on the upper side thereof,the shape of said gas-permeable member essentially coinciding with thewave front produced by said sound transmitter.

3. Apparatus as claimed in claim 2, wherein said gas-permeable memberconsists of a frustoconical upper cap projecting from the upper side ofthe sloping member.

4. Apparatus as claimed in claim 1, wherein said lower cap provided onthe lower side of the sloping member consists of a frustoconical capprojecting from the lower side of the last said member.

5. Apparatus as claimed in claim 4, wherein said upper and lower capsare rigidly fixed to said sloping member concentrically with saidopening.

6. Apparatus as claimed in claim 1, further comprising a pipe stubextending from said lower cap and said sound transmitter and resonatorhorn being disposed inside said pipe stub and directed toward thechamber formed by said lower cap and said gas-permeable member.

7. Apparatus as claimed in claim I, further comprising a gas lineconnected to said chamber formed by said lower cap and saidgas-permeable member for supplying gas to the chamber for dischargethrough said gas-permeable member.

1. Apparatus for initiating and facilitating the sliding of particulatematerial along an essentially plane sloping surface, comprising acontainer having a bottom outlet and a resilient sloping memberadjoining said outlet and forming said surface, said member having anopening spaced from the defining margins thereof, a lower cap rigidlyfixed to the lower side of said member and carried thereby, said lowercap underlying and closing said opening, a gas-permeable member coveringsaid opening on the upper side of said sloping member, saidgas-permeable member and said lower cap defining a chamber, and a soundtransmitter carried by said lower cap, said sound transmitter openinginto said chamber and being directed toward said gas-permeable member toactivate said material by loosening and activating the material by meansof sound oscillations produced by said sound transmitter, said lower capand said gas permeable member imparting sonic vibrations to saidresilient sloping member which thereby forms a diaphragm further aidingin the movement of said particulate material.
 2. Apparatus as claimed inclaim 1, wherein said gas-permeable member forms a supporting surfacefor the material on the upper side thereof, the shape of saidgas-permeable member essentially coinciding with the wave front producedby said sound transmitter.
 3. Apparatus as claimed in claim 2, whereinsaid gas-permeable member consists of a frustoconical upper capprojecting from the upper side of the sloping member.
 4. Apparatus asclaimed in claim 1, wherein said lower cap provided on the lower side ofthe sloping member consists of a frustoconical cap projecting from thelower side of the last said member.
 5. Apparatus as claimed in claim 4,wherein said upper and lower caps are rigidly fixed to said slopingmember concentrically with said opening.
 6. Apparatus as claimed inclaim 1, further comprising a pipe stub extending from said lower capand said sound transmitter and resonator horn being disposed inside saidpipe stub and directed toward the chamber formed by said lower cap andsaid gas-permeable member.
 7. Apparatus as claimed in claim 1, furthercomprising a gas line connected to said chamber formed by said lower capand said gas permeable member for supplying gas to the chamber fordischarge through said gas-permeable member.